After hearing rave reviews from his friends, Scott Cover decided it was time to try the pizza at Joe Squared himself. But after a lackluster pie and what he considered overpriced beers, Cover felt the popular Station North restaurant had fallen well short of his expectations.

"Initially, I was severely let down," Cover, a 31-year-old information technology consultant, said recently of his March 2010 outing. "It was like, 'This isn't as awesome as everyone makes it seem.'"

Then the Federal Hill resident did what many customers do after a bad experience: He turned on his computer and wrote about it.

"The sauce was horribly bland, and I couldn't even taste it as it was simply overpowered by everything else on the pizza," Cover wrote.

His critique wasn't posted on Facebook or Twitter, but Yelp, the increasingly popular website that serves as a public compilation of user-generated reviews (more than 33 million) and a social media community full of opinionated shoppers. The site receives an average of 84 million unique visitors per month, according to Darnell Holloway, Yelp's manager of local business outreach.

But really, Yelp — and other review sites such as Angie's List and Google Places — are websites where everyone is a critic. The writers may lack credentials, but they lack an editor, too, which allows their reviews to be as harsh or as glowing as they see fit. Customers have always wielded the influence to potentially make or break a business through word of mouth, but Yelp takes it a step further by neatly compiling reviews on an easy-to-find website. While the power is in the hands of the customer, businesses take these reviews seriously, too: They're firing staff members based off complaints, and reaching out to unsatisfied customers with free incentives in hopes of getting a second chance.

There are even lawsuits over negative online reviews. After giving a one-star review to an alleged "nightmare" of a contracting job, Fairfax, Va.'s Jane Perez was sued by the contractor for $750,000 in an Internet defamation lawsuit. A hearing will be held today, according to The Washington Post.

While Holloway declined to provide Maryland-specific statistics, it's safe to say Yelp has a sizable audience in the area. There are more than 1,700 restaurants in the Baltimore area with Yelp pages. Woodberry Kitchen, which has been written about most, has more than 500 reviews.

"If you look at our traffic growth, it's been pretty phenomenal over the past few years," Holloway said.

It has never been easier to publicly laud or skewer a local business. Anyone with an Internet connection or smartphone can affect a company's reputation, whether it's a hair salon, restaurant, physician or general contractor. And the reviews can make an impact: Last year, a study published in the Economic Journal suggested a half-star on Yelp could swing a restaurant's reservation availability by 19 percent.

Cover's story of pizza letdown could have ended with his review, but because Joe Squared's owner Joe Edwardsen checks his Yelp pages (he has a second one for his Power Plant Live restaurant) once per week, he read the two-star (out of five) review shortly after it was published. As he does with all negative online reviews he considers reasonable, Edwardsen sent Cover a message through Yelp, offering a free meal as an apology.

"I just want to change their mind," Edwardsen said. "I want to find some way to actually please them. I don't want them to feel like we took advantage of them."

This type of back-and-forth exchange happens often on Yelp, and it helps illustrate why the website has become so popular in recent years. (The publicly traded company posted $83.3 million in revenue in 2011, up nearly 75 percent from the previous year, according to Forbes.) While the main goal of Yelp and similar sites — besides making a profit — is to better inform consumers before spending their money, engaged businesses stand to benefit, too.

Edwardsen says negative comments about specific staff members "have been the icing on the cake to someone getting fired."

"I've heard a lot of customer complaints that have led to productive changes to the restaurant through Yelp," Edwardsen said. "No one would have said it directly to my face, but they'll post it on that site."

That influence and power isn't lost on Amber Patterson, general manager of Zina's Day Spa of Canton. While she says a referral from a friend to a new customer remains the most effective way to expand business, a positive review online is "the next best thing." Zina's employees encourage satisfied clients ("the ones that rant and rave" as they leave, Patterson says) to write online reviews.

"Absolutely, it's a big thing," Patterson said. "Their goal is to get people to come back, so I encourage them all of the time to discuss reviews."

But what if those opinions can't be read easily?

Before publication, a Yelp review must make it past an automated "filter" system. While it is Yelp's policy not to discuss how the system works, Holloway says 20 percent of all reviews are filtered into a separate section of the site, including both legitimate reviews and fake ones written to try and "game the system."

"It's the high cost we're willing to accept," he said.

Samantha Satchell, creator and owner of the Owings Mills-based fitness program Maverick Dance Party, ran into this problem last month.

At the recommendation of a Living Social employee, Satchell created a Yelp page in December. Looking to partner with the online coupon company for a Maverick-related deal, Satchell was told a Yelp page could improve the offer's chances of approval. So she asked a number of regular customers to write reviews, and many happily obliged. ("I talk about her to other people I know anyway, so this was another way to get it out there," said Anna James, a 26-year-old customer from Lutherville.)

But the Maverick Dance Party Yelp page is barren of user-generated content. To read the 14 posts — all fawning, five-star reviews from first-time reviewers — from Satchell's students, you must find the page of "filtered reviews," an arguably easy-to-miss link. Then, a user must enter a two-phrase "reCAPTCHA" code before gaining access to the reviews.

The filtering process soured Satchell on Yelp.

"I asked these people to do me a favor and they did, and they weren't heard," Satchell said. "It makes the whole process look really bad. It's unprofessional."

While Yelp's website says businesses should "probably not" explicitly ask customers to write reviews, it does not explain how the filtering system works. Holloway says there is a misconception that the automated system (which, he says, "has some of the best engineering minds in Silicon Valley" regularly tweaking it) filters out only positive reviews, but that is not the case. It does filter out more positive than negative reviews because, according to Yelp, 80 percent of the reviews are rated three stars or higher.

When asked for details regarding the system's process, he declined, due to security reasons.

"We don't publicly disclose what makes the filter work," Holloway said. "It would defeat the process. There are people trying to adjust and reverse the system. But I can tell you the same set of rules are being put across Yelp's systems."

A major criticism against Yelp is its seemingly anonymous reviews. While you must create a Yelp account with a valid email address to contribute reviews, there's no guarantee the user provided his or her real name. For some consumers, that makes the subscription-based website Angie's List an attractive alternative.

With nearly 30,000 subscribers in the Baltimore area (and more than 1.5 million in America), Angie's List requires users to provide personal information, including a home address, to validate a new account. Upon submitting a review, a user will be reminded that his or her name and address will be shared, upon request, with the business that was reviewed.

Angie's List — whose yearly subscription costs $35 in Baltimore — places a premium on accountability for both its businesses and users. For this reason, it has never considered publishing anonymous reviews, according to Cheryl Reed, director of communications.

"Over the years, corporate leadership has looked at just about everything, but never have we considered going anonymous," Reed said. "It weakens the veracity of the information, and we're not willing to do that. Our members believe it's worth the price of admission." (Angie's List's third quarter revenue report from 2012, which showed a year-to-date increase of 75 percent to $109.6M, supports this claim.)

While the two companies differ on access fees, Angie's List and Yelp are both adamant that businesses cannot pay money — through sponsorship or otherwise — to remove or change the order of negative reviews.

Regardless of which sites consumers choose to use, the growing prominence of Yelp, Angie's List and online reviews in general is hard to ignore.

Amy Burke Friedman, vice president of the Baltimore public relations agency Profiles, Inc. — whose clients include Ra Sushi Bar Restaurant, B&O American Brasserie and the Maryland Athletic Club & Wellness Center — says she stresses to clients the importance of heightening their Internet presences through not only Facebook and Twitter, but also Yelp and Urbanspoon, a similar site.

"People who participate in Yelp are an audience we really value, and we stress to restaurants to care," Friedman said. "That's customer feedback that should be taken seriously, whether it's positive or negative. It's an opportunity to learn and grow."

Richard Lee, a Fells Point resident and active Yelp-er who describes his reviews as "self-contained short stories," says these sites help consumers make better-informed decisions, especially in Baltimore, where there's no shortage of competition.

"People deserve to know because there are so many places to go," Lee, 31, said. "These businesses need to fight for your money every day."

Edwardsen — who ultimately deciding against, but considered, paying public relations companies to write positive reviews after his own frustrations with Yelp's filter system — agrees, albeit begrudgingly.

"I hate Yelp," Edwardsen said with a laugh. "But we're a much better restaurant than we would be if Yelp weren't around."